use of activated carbon in supercapacitor .... it consists carbon electrode having high surface area & porosity.

1. ROLE OF ACTIVATED CARBON IN
SUPERCAPACITOR
1 By - Kinjal

2. WHAT IS A SUPERCAPACITOR?
 It can be defined as a energy storage device that stores energy
electrostatically by polarizing an electrolytic solution.
 Electrochemical Double Layer Capacitors (EDLCs) – also called
supercapacitors (SC) - are electrochemical capacitors that have
high capacitance and high energy density when compared to
common capacitors, and higher power density when compared to
batteries.
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3. PRINCIPLE
Energy is stored in ultracapacitor by polarizing the electrolytic
solution. The charges are separated via electrode –electrolyte
interface.
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Electrolyte
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4. CONSTRUCTION
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5. CONSTRUCTION
 Most EDLC's are constructed from:
 two carbon based electrodes (mostly activated carbon with a
very high surface area),
 an electrolyte (aqueous or organic) and
 a separator (that allows the transfer of ions, but provides
electronic insulation between the electrodes).
 As voltage is applied, ions in the electrolyte solution diffuse across
the separator into the pores of the electrode of opposite charge.
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6. WORKING
 When the voltage is applied to positive plate, it attracts
negative ions from electrolyte.
 When the voltage is applied to negative plate, it attracts
positive ions from electrolyte.
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7. WORKING
 Charge accumulates at the interface between the electrodes and
the electrolyte (the double layer phenomenon that occurs
between a conductive solid and a liquid solution interface),
and forms two charged layers with a separation of several
angstroms – the distance from the electrode surface to the
center of the ion layer .
 The double layer capacitance is the result of charge separation
in the interface.
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8. SUPERCAPACITOR
 Since capacitance is
proportional to the surface
area and the reciprocal of the
distance between the two
layers, high capacitance
values are achieved.
 C = k A / d
Where, C – capacitance,
k- Dielectric constant of
medium
A - area of the plate
d- Distance between the plates
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9. SUPERCAPACITOR
 Using activated carbon which has large surface area for
electrodes, enables EDLC to have high capacitance.
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10. ACTIVATED CARBON
 Activated Carbons are the most powerful adsorbents known.
 It is basically a solid material consisting mainly of pure carbon.
 A characteristic feature is its porous structure and the resulting
immense surface area which may be as large as 1500 m2/gm.
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11. ACTIVATED CARBON
 Activated carbons work on the principle of adsorption.
 Adsorption is an interfacial process involving the collection of
gaseous or solute components on the surface of adsorbent solids.
 Adsorption is thus a physical process, i.e. the substances adsorbed
on the solid do not undergo any chemical reaction with the latter.
 The adsorbing solid is referred to as adsorbent and the substance
to be adsorbed from the liquid or the gas phase as the solute is
referred to as adsorbate.
 The adsorption power and rate is determined by the kind of
activated carbon, the particle size, the pore size and its
distribution.
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12. The vast increases in capacitance achieved by
supercapacitors are due to the combination of:
(i) an extremely small distance that separates the opposite
charges, as defined by the electric double-layer;
(ii) highly porous electrodes that embody very high
surface-area.
variety of porous forms of carbon are currently preferred
as the electrode materials because they have
•exceptionally high surface areas,
•relatively high electronic conductivity, and
•acceptable cost.
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13. Electrode material characteristics
The attraction of carbon as a supercapacitor electrode
material arises from a unique combination of chemical
and physical properties, namely:
• high conductivity,
• high surface-area range
• good corrosion resistance,
• high temperature stability,
• controlled pore structure,
• relatively low cost.
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14. GREEN TECHNOLOGY SUPER CAPACITORS
 Activated carbon used is unsustainable and expensive.
 Biochar is viewed as a green solution to the activated carbon
currently used in super capacitor electrodes.
 Unlike activated carbon, biochar is the byproduct of the pyrolysis
process used to produce biofuels and it is nontoxic and will not
pollute the soil when it is tossed out.
 Biochar costs almost half as much as activated carbon, and is
more sustainable because it reuses the waste from biofuel
production, a process with sustainable intentions to begin with.
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